Add API for extracting image size from a file

For the asynchronous loading we need a function call that parses
a file, given its path, and retrieves the image width and height.

This commit adds cogl_bitmap_get_size_from_file() to the CoglBitmap
API.

cogl-texture.h

@@ -415,10 +415,27 @@ void            cogl_texture_polygon          (CoglHandle          handle,
  *
  * Returns: A #CoglBitmap to the new loaded image data, or %NULL if loading 
  * the image failed.
+ *
+ * Since: 1.0
  */
 CoglBitmap *    cogl_bitmap_new_from_file     (const gchar    *filename,
                                                GError        **error);
 
+/**
+ * cogl_bitmap_get_size_from_file:
+ * @filename: the file to check
+ * @width: return location for the bitmap width
+ * @height: return location for the bitmap height
+ *
+ * Parses an image file enough to extract the width and height
+ * of the bitmap.
+ *
+ * Since: 1.0
+ */
+gboolean        cogl_bitmap_get_size_from_file (const gchar   *filename,
+                                                gint          *width,
+                                                gint          *height);
+
 /**
  * cogl_bitmap_free:
  * @bmp: a #CoglBitmap.

common/cogl-bitmap-pixbuf.c

@@ -84,6 +84,20 @@ cogl_bitmap_error_quark (void)
   return g_quark_from_static_string ("cogl-bitmap-error-quark");
 }
 
+gboolean
+_cogl_bitmap_get_size_from_file (const gchar *filename,
+                                 gint        *width,
+                                 gint        *height)
+{
+  if (width)
+    *width = 0;
+
+  if (height)
+    *height = 0;
+
+  return TRUE;
+}
+
 /* the error does not contain the filename as the caller already has it */
 gboolean
 _cogl_bitmap_from_file (CoglBitmap  *bmp,
@@ -177,9 +191,22 @@ _cogl_bitmap_from_file (CoglBitmap  *bmp,
 #elif defined(USE_GDKPIXBUF)
 
 gboolean
-_cogl_bitmap_from_file (CoglBitmap  *bmp,
-			const gchar *filename,
-			GError     **error)
+_cogl_bitmap_get_size_from_file (const gchar *filename,
+                                 gint        *width,
+                                 gint        *height)
+{
+  g_return_val_if_fail (filename != NULL, FALSE);
+
+  if (gdk_pixbuf_get_file_info (filename, width, height) != NULL)
+    return TRUE;
+
+  return FALSE;
+}
+
+gboolean
+_cogl_bitmap_from_file (CoglBitmap   *bmp,
+			const gchar  *filename,
+			GError      **error)
 {
   GdkPixbuf        *pixbuf;
   gboolean          has_alpha;
@@ -198,11 +225,13 @@ _cogl_bitmap_from_file (CoglBitmap  *bmp,
   
   g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
 
-  if (bmp == NULL) return FALSE;
-  
+  if (bmp == NULL)
+    return FALSE;
+
   /* Load from file using GdkPixbuf */
   pixbuf = gdk_pixbuf_new_from_file (filename, error);
-  if (pixbuf == NULL) return FALSE;
+  if (pixbuf == NULL)
+    return FALSE;
   
   /* Get pixbuf properties */
   has_alpha       = gdk_pixbuf_get_has_alpha (pixbuf);
@@ -278,6 +307,20 @@ _cogl_bitmap_from_file (CoglBitmap  *bmp,
 
 #include "stb_image.c"
 
+gboolean
+_cogl_bitmap_get_size_from_file (const gchar *filename,
+                                 gint        *width,
+                                 gint        *height)
+{
+  if (width)
+    *width = 0;
+
+  if (height)
+    *height = 0;
+
+  return TRUE;
+}
+
 gboolean
 _cogl_bitmap_from_file (CoglBitmap  *bmp,
 			const gchar *filename,
@@ -290,11 +333,15 @@ _cogl_bitmap_from_file (CoglBitmap  *bmp,
 
   g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
 
-  if (bmp == NULL) return FALSE;
+  if (bmp == NULL)
+    return FALSE;
   
   /* Load from file using stb */
-  pixels = stbi_load (filename, &width, &height, &stb_pixel_format, STBI_rgb_alpha);
-  if (pixels == NULL) return FALSE;
+  pixels = stbi_load (filename,
+                      &width, &height, &stb_pixel_format,
+                      STBI_rgb_alpha);
+  if (pixels == NULL)
+    return FALSE;
  
   /* Store bitmap info */
   bmp->data = g_memdup (pixels, height * width * 4);

common/cogl-bitmap.c

@@ -149,6 +149,14 @@ _cogl_bitmap_copy_subregion (CoglBitmap *src,
     }
 }
 
+gboolean
+cogl_bitmap_get_size_from_file (const gchar *filename,
+                                gint        *width,
+                                gint        *height)
+{
+  return _cogl_bitmap_get_size_from_file (filename, width, height);
+}
+
 CoglBitmap *
 cogl_bitmap_new_from_file (const gchar    *filename,
                            GError        **error)

common/cogl-bitmap.h

@@ -90,4 +90,9 @@ _cogl_bitmap_copy_subregion (CoglBitmap *src,
 			     gint        width,
 			     gint        height);
 
+gboolean
+_cogl_bitmap_get_size_from_file (const gchar *filename,
+                                 gint        *width,
+                                 gint        *height);
+
 #endif /* __COGL_BITMAP_H */